The crests are the peak heights of the wave and the troughs are the lowest valleys.
A wave is described by its wavelength (or the distance between two sequential crests or two sequential troughs), the wave period (or the time it takes a wave to travel the wavelength), and the wave frequency (the number of wave crests that pass by a fixed location in a given amount of time).
When a wave travels, it is passing through the water, but the water barely travels, rather it moves in a circular motion.
